PURPOSE:To enhance measuring efficiency by simultaneously measuring the thickness of a heat transfer pipe and the outer surface state thereof, by using the jigs arranged along the outer surface of the heat transfer pipe at a predetermined interval and the electromagnetic ultrasonic sensor, which is equipped with a magnetic field and a transmitting-receiving coil, provided along the jigs. CONSTITUTION:When the thickness of a heat transfer pipe 1 is measured by an ultrasonic wave while an electromagnetic ultrasonic sensor 3 is moved in the order of A, B, C, D and E, the thickness of the part to be measured is measured at the time interval T of echo reflection but the degree of the configurational change of the pipe on the inner and outer sides thereof can not be judged. Herein, when a pulse current is allowed to flow to a transmitting- receiving coil 5, an eddy current 7 is generated on the surface of the pipe 1 opposed to the coil 5 by electromagnetic induction action. An ultrasonic wave passes through the wall part of the pipe 1 to reach the interior thereof and subsequently reflects therefrom to return to the outer surface of the pipe. The reception of the returned ultrasonic wave is performed by the action reverse to that at the generation time of the ultrasonic wave. By this method, the interval from the surface of a jig to the surface of the pipe 1 can be measured and the outer and inner surface shapes of the pipe 1 can be measured on the basis of the surface of the jig.
